The standard route is through Guild fences or by achieving a high-level speech perk that allows you to do so. I'm not a big fan of the speech perks, though - by the time you get to the high-level benefits, you don't really need them anymore - and Guild fences are few and far between even after going through the Guild quest line.

An alternative, for the skilled pickpocket, is to reverse-pickpocket your stolen items onto bandits or other enemies. Then kill them. Then take your legitimately-earned loot, without 'stolen' tags, from the corpse.